RE: Move the injection_points extension to contrib?

Dear Antonin,

> Having the extension in contrib would be useful in cases a 3rd party extension
> uses injection points in its regression tests. In particular, it's more
> practical for CI to install the "injection_points" extension by installing the
> "contrib" binary package than by building the whole server from source. (AFAIK
> the src/modules/injection_points directory is currently not included in any
> package.)

IIRC, one of the motivation why we put src/test/modules is to ensure the flexiblity.
Even contrib modules must follow the rule [1]. E.g., ABI must be kept and API
change should be considered carefully - commits like [2] may be restricted.
Also We may even have to consider that whether the name of injection points
should be kept or not.

How do you feel?

[1]: https://www.postgresql.org/docs/devel/xfunc-c.html#XFUNC-GUIDANCE-API-COMPATIBILITY
[2]: https://github.com/postgres/postgres/commit/f4af4515bb5f3591d49bc16b6cb8ddbf66f98374

Best regards,
Hayato Kuroda
FUJITSU LIMITED